Testing safety ECUs at an early stage

Manufacturers of safety-critical electronic control units (ECUs) face increasingly complex questions due to the rapid proliferation of sophisticated technology installed in vehicles, as well as consistently growing demands and legal requirements to be met by safety ECUs.

The requirements of ISO 26262 ("Road Vehicles—Functional Safety"), which primarily apply to safety-relevant electronic systems in motor vehicles, are relevant in this context. Other important requirements are those established by the Euro NCAP organisation, as their evaluation plays a major role in the consumers' acceptance of vehicles.

On the technological side, solutions for increasingly challenging performance requirements have to be found as well. This requires highly complex sensors and the sharing of information from these sensors across various ECUs.

The following look at vehicle safety shows the importance of this topic and illustrates that this major development trend will continue in the future.

Requirements for safety ECUs
The number and complexity of test cases are without doubt increasing in the field of vehicle safety as well. By means of various crash sensors installed in different places of the vehicle (see schematic depiction in Figure X) airbag control units have to decide if, when, and if so, which of the airbags should be ignited for deployment.

Another typical question that arises in this context is the optimisation of the ignition timing for airbag inflators. Decisions derived on the basis of sensor information and the determination of the optimum safety response can have far-reaching consequences and may make the difference between life and death.

Interaction of safety systems and advanced driver assistance systems
To satisfy relevant safety requirements, a large number of ECUs and sensors that analyse the environment are installed in modern vehicles, a trend that will continue to grow. Advanced driver assistance systems (ADAS) are used to recognise dangerous situations early in order to avoid accidents. Passive safety systems such as belt tensioners and airbags serve to mitigate the consequences of accidents. In contrast to passive systems, active safety systems such as the emergency brake assist intervene with the vehicle's operation at an early stage in order to avoid a collision.

Advanced driver assistance systems obtain their environmental information from various sensor sources. The fusion of environment and crash sensors (figure 1) and the exchange of radar, lidar, camera, ultrasound and vehicle dynamics data, for example, open up completely new possibilities in the field of safety.

By means of ADAS, critical scenarios can be detected and classified in advance. This results in a valuable gain of time which can be used to initiate preliminary safety responses even before the crash sensors are able to detect anything.

But even in scenarios that do not involve the deployment of airbags, such as rear-end collisions in urban traffic, occupant protection measures can be initiated by means of belt tensioners. They restrain the occupant in an optimal position prior to contact with another vehicle and thus help to mitigate the consequences of an accident.